


HOW TO USE 



Portland Cement 



From the German of L. GOLINKLLI. 

Published under the name of ^^ Das Kleine Cement- Buck ^'^ 
by the Association of German Portland 
• Cement Manufacturers. 



Translated by 

SPENCER B. NEWBERRY, E. M. Ph. D., 

Acting Professor of Chemistry, Cornell University, 1887-1S92. 

U. S. Commissioner to Paris Exposition, 1889 

Judge, Chicago Exposition, 1893. 



Copyrighted by W1LI.IAM SeaFERT, 
1899 

THIRD EDITION 1904 



Price^ Fifty Cents* 



LA '4 



Cement and Engineering News 
CHICAGO, 



IN PREPARATION 



TREATISE ON 



Armored Concrete Constructions 

With General Applications under the Various Systems in use in the United States and 
Europe, with numerous illustrations and calculations. 

BY E. I_EE HEIDENFIEIC^H 

Member American Institute Mining Engineers aud Western Society of Engineers. 

[Copyright 1903] 



SYNOPSIS OF 

Chapter I. Abbreviated history. 

Chap. II. Cause of the extraordinary de- 
velopment of Armored Concrete. 

Chap. III. Illustrated applications of the 
principal systems of Floor Constructions, 
Beams, Girders and Foundations. 

Chap. IV. Illustrated application of the 
principal systems of Culverts, Pipes and Tun- 
nel Construction, 

Chap. V. Tanks and Reservoirs. 

Chap. VI. Cluster Construction, G''ain 
Elevators, Cement and other storage. 

Chap. VII. Retaining Walls, Docks and Chap. XIX 

Wharves. Chap. XX. 

Chap. VIII. Arches and Domes. Appliances 

Chap. IX. Bridges. Chap. XXI. 

Chap, X. Stairs, Grand Stands, Etc. Construction 

Chap. XI. Manufactured Articles, Fence Chap. XXII 

Posts, Smoke Jacks, Coffins, Tubs, Small Cul tails 
vert and Sewer Pipe, etc. Chap. XXIII 

Chap. XII. Application of Moulds and Chap. XXIV 



CONTENTS. 

Chap. XIII. General notes on the Relative 
and Combined Strength of Steel and Concrete. 

Chap. XIV. Calculation of Floor Beams 
and Girders. 

Chap. XV. Calculation of Columns and 
Piers. 

Chap. XVI. Calculation of Pipes, Culverts, 
Arches and Domes. 

Chap. XVII. Calculation of Tanks, Re- 
servoirs and Clusters. 

Chap. XVIII, Calculation of Retaining 
Walls. 

Calculation of Bridges. 
Practical Details, Tools and 

Cost of Armored Concrete 

Miscellaneous Practical De- 



General Conclusion. 
Index. 



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HOW TO USE 



Portland Cement. 



From the German of L. Golinelli. 



Published under the name Das kleine Cement-buch by the Association of 
German Portland Cement Manufacturers. 



Translated by Spencer B. Newberry. ",€, Ilewbvvrv) 



[Copyrighted by William Seafert.] 
1899. 



CHICAGO: 

CEMENT AND ENGINEERING NEWS, 

190S. 



-- St 



.Gr6z 



6 







PREFACE. 



A few years ago a very important and useful book, 
"Der Portland-cement und seine Anwendungen im 
Bauwesen," (Berlin, 1892), was published by the Asso- 
ciation of German Portland Cement Manufacturers. 
This work includes the best information obtainable in 
reference to the testing and uses of Portland cement, 
and contains numerous illustrations showing the details 
of important examples of engineering work in which 
cement was employed. The cordial reception given 
this book by educated engineers led the association 
to undertake the preparation of a small pamphlet on 
the same subject, intended chiefly for the use of con- 
tractors and masons, which should give in simple and 
practical form the results of the best experience in the 
use of Portland cement. This pamphlet has lately been 
issued under the title of " Das Kleine Cement-buch,'' 
by the publishers of the Thonindusii'ie Zeitung. Over 
22,000 copies were sold in Germany during the past 
few months, and a new edition has already been ordered. 

Germany has long led the world in knowledge of 
the applications of cement, and most of our best 
information in regard to methods of manufacture, 
testing and uses of cement has come from that coun- 
try. A full translation of this little pamphlet, repre- 
senting, as it does, the latest German thought on the 
subject, will therefore doubtless be of interest to Amer- 
ican cement consumers. 

S. B. N. 
Sandusky, O., March, 1899 



HOW TO USE PORTLAND CEMENT. 



From the German of L. Golinelli. 

(Published under the name Daskleine Cement-buchhj the Asso- 
ciation of German Portland Cement Manufacturers.) 

Translated by S. B. Newbbbby. 

It is an established fact that Portland cement is 
superior to all other hydraulic materials, natural or 
artificial, and for this reason it is widely distributed 
throughout the world. Its use would, however, be far 
greater if the knowledge of the applications and meth- 
ods of testing of cement had kept pace, during the past 
ten years, with the improvements which have been 
made in quality and methods of manufacture. Even 
in sections where the manufacture of Portland cement 
has been extensively and successfully developed, and 
where one would consequently expect to find a certain 
amount of knowledge of the subject, a correct under- 
standing of methods of testing and intelligent use of 
cement is often painfully lacking. The preparation and 
use of cement mortar, as practiced in many cases by 
masons or their helpers, is not only imperfect but 
wasteful. Better work could often be done with less 
material if careful methods were used. In the case of 
Portland cement such careful methods are especially 
necessary and profitable, and if thej^ were followed the 
common complaint that Portland cement is too expens- 
ive would soon be no longer heard. Those who do 
intelligent and careful work have for a long time recog- 
nized the injustice of this charge. On the other hand, 
it is undoubtedly true that a high-grade material like 



6 PBOPEBTIES OF PORTLAND CEMENT. 

Portland cement, which in skillful hands may be use- 
fully and economically employed for an immense vari- 
ety of purposes, is especially liable to suffer from ignor- 
ance and misuse. 

I. PROPERTIES OF PORTLAND CEMENT. 
DEFINITION AND MANUFACTURE. 

Portland cement is a material which hardens in the 
presence of water, prepared by burning at a sintering 
temperature an intimate mixture consisting essentially 
of lime (or carbonate of lime) and clay in certain defin- 
ite proportions. 

The raw materials, clay and carbonate of lime, are 
ground and mixed according to their character in either 
the wet or dry way. If the dry process is used, the 
mixed materials are moistened with water and molded 
into blocks. In the wet process the bricks are made 
from the wet material after it has been reduced to the 
proper consistency. After drying, the bricks of cement 
material are burned in suitable kilns to the point of 
sintering. The resulting "clinker" is ground to a fine 
powder; this is the finished cement. 

CHEMICAL COMPOSITION. 

The raw materials indicate the nature of the constit- 
uents of Portland cement. These are silica, alumina, 
iron oxide, lime and a small amount of magnesia. 
Alkalies and sulphates are are also always present, and 
are derived from the raw materials, which are never 
found pure in nature. 

The presence of sulphuric acid (sulphate of lime) is 
also due to the sulphur in the fuel employed, and to 
the addition of a small amount of gypsum (sulphate of 
lime) for the purpose of making the cement slow-setting. 



CHEMICAL COMPOSITION. 7 

The composition of good Portland cement usually 

Taries between the following limits: 

Lime 58 to 65 per cent 

Silica 20 to 26 

Alumina 7 to 14 

Magnesia 1 to 3 

Alkalies traces to 3 

Sulphuric Acid traces to 2 

According to the character of the raw material used, 
each manufacturer determines the correct composition 
of his product within the above limits, and this com- 
position must be kept uniform by constant chemical 
analysis. The widespread belief that defective quality 
of cement is due to bad raw materials is seldom well 
founded; the fault is generally due to incorrect propor- 
tions and careless manufacture. 

In studying the qualities of Portland cement, the 
following points are to be especially noted : 

1. Form and fineness of grain. 

2. Color and specific gravity. 

3. Time of setting. 

4. Hardening. 

5. Strength. 

6. Constancy of volume. 

7. Hair cracks and shrinkage cracks. 

8. Behavior under under extreme heat and cold. 

9. Additions and adulterations. 

FORM AND FINENESS OF GRAIN. 

When examined under the microscope, particles of 
hydraulic lime have a more or less rounded form. 
Portland cement, on the other hand, shows thin leaf- 
lets of shale-like structure, like pounded glass. The 
high quality of Portland cement is in part due to this 
shale-like character, since greater density of mortar 



8 COLOR AND SPECIFIC GRAVITY. 

results from the greater surface of contact and smaller 
proportion of voids between the particles. 

As to fineness of grinding, it may be mentioned that 
the coarser particles of cement act practically like sand. 
It is therefore important that the grinding be not too 
coarse. A residue of not more than 5 per cent on a 
sieve of 75 meshes to the linear inch may fairly be 
demanded. The finer the grinding, the more sand can 
be used with the cement. It should be remembered, 
however, that poor cements, especially those too high 
in clay or imperfectly burned, are especially easy to 
grind to great fineness. Such cements may be gener- 
ally recognized by their yellowish color and the spotty 
appearance of the work. 

COLOR AND SPECIFIC GRAVITY. 

The color of Portland cement should be a greenish 
gray; a yellowish or reddish gray tint indicates gener- 
ally an inferior, light-burned product, or one to which 
under-burned or " dusted " material has been added. 

Portland cement has a high specific gravity, a quality 
which contributes to its high value. No other hydraulic 
material has so high a specific gravity, or yields so 
dense and resistant a mortar. The specific gravity of 
Portland cement is from 3.12 to 3.25. 

TIME OF SETTING. 

When Portland cement is mixed with a suitable qual- 
ity of water, a plastic paste is produced, which after a 
time becomes hard. The change from a semi-liquid to 
a solid mass is called setting, and the time required for 
%is change, the time of setting. Cement is said to be 
set when it resists a light pressure of the finger nail on 
the surface. 



TIME OF SETTING. 9 

It is of the greatest importance to know the time 
of setting of a cement which it is proposed to use, since 
a cement which has become set and has been again 
mixed up with water possesses little or no hydraulic 
energy. The mistake of mixing "set*' mortar anew 
with water occurs only too often, and gives rise to the 
unjust complaint that the cement does not harden or 
possesses no strength. Great care should therefore be 
taken to mix up only such a quantity of mortar as can 
be conveniently used up in the time available; this can 
be easily managed when the time of setting is known. 

Remnants of mortar which have become set should he 
discarded and must under no circumstances he again 
worked up with water. 

The determination of the time of setting is extremely 
simple, and may be made by any mason at the place 
where the cement is used. The best method is as fol- 
lows: 

The cement is mixed with water to a thick paste, 
worked one to two minutes with a spoon or trowel and 
spread out in the form of a pat on a glass plate. This 
pat should be about one-half inch thick in the middle 
and thin at the edges. As soon as the surface resists a 
light pressure of the finger-nail the cement is set. 
Since the temperature and the proportion of water 
used are of great influence on the result, it is best to 
have the cement and water at the ordinary temperature 
of 60 to 70 degrees, and to use not more than 30 to 32 
per cent of water. The water must be clean. The pat 
should be protected from sunshine and drafts of air. 

It is in the power of the manufacturer to produce 
either quick-setting or slow-setting cement, as may be 
required. A cement which requires two hours or longer 
to set is called slow-setting. Such cement is preferable 



10 HARDENING. 

to that which sets quickly, on account of its greater 
strength. Quick-setting cement is used only for cer- 
tain special purposes. Slow-setting cement can be 
made to set more quickly by using warm water, and 
also by limiting the water used to the smallest possible 
quantity. Among the substances which modify the 
time of setting may be mentioned: 

Potash and soda, which hasten the setting. Sulphates 
and calcium chloride, which retard the setting. 

In all cases the consumer will do well to notify the 
manufacturer what time of setting is desired, also for 
what purpose the cement is to be used. In this way 
many unjust complaints in regard to quality and many 
unnecessary expenses may be avoided. 

HARDENING. 

The set cement is capable of hardening^ either in 
water or in air, and in a short time will acquire a high 
degree of strength. The processes of setting and hard- 
ening should not be confused. The latter begins at the 
point where the former ceases, and continues up to the 
highest strength which the cement attains after the 
lapse of many years. 

As to the nature of the hardening process, to account 
for which various theories have been advanced, it need 
only be here stated that the hardening consists in chem- 
ical combination with water taking place under certain 
physical conditions. Among the most important of 
these conditions are rest during the setting and protec- 
tion from too rapid drying out. The latter point can 
not be too strongly insisted upon. If the cement is 
deprived of the necessary water it can never reach its 
full hardness. 



STRENGTH. 11 

Portland cement attains within a few days a high 
degree of strength. 

In the use of cement for building purposes, compres- 
sion strength is the quality generally required. Cement 
is, however, generally tested only for tensile strength, 
owing to the fact that the tests of tensile strength can 
be made much more quickly, simply and cheaply than 
those of compression. There is also a definite, (though 
by no means exact) relation between the two tests, the 
compression strength being generally from 8 to 12 
times the tensile strength. 

The German official standards for Portland cement 
require that a mixture of one part cement with three 
parts normal sand shall show a tensile strength at 28 
days of at least 227 lbs. per sq. in. 

It is by no means simple, however, to make tensile 
strength tests in such a manner as to give reliable 
results. Complaints in regard to the quality of cement 
are often due entirely to faulty testing. In the prepar- 
ation of briquettes, the temperature and quantity of the 
water used, the character of the sand employed, and 
the thoroughness with which the mortar is worked, are 
of immense influence on the results. The strength will 
generally be greater the less water is used; nevertheless 
it is always necessary to use such a quantity of water 
that it shall show itself on the surface of the briquette 
on tamping it into the mold. Long and vigorous work- 
ing of the mortar increases its strength. In extensive 
building operations the use of mixing machines, especi- 
ally pans with edge runners, is therefore highly advan- 
tageous. 

CONSTANCY OF VOLUME AND CRACKING. 

Strictly speaking, there is no such thing as constancy 
of volume, either in the case of mortar or stone, since 



12 CONSTANCY OF VOLUME AND CRACKING. 

heat and cold, wetting or drying, modify the volume 
more or less. Portland cement also suffers changes of 
volume on hardening in water or in air. In the case of 
good Portland cement, however, these changes are 
extremely small and much less than those which occur 
in different kinds of stone. Bad cements, on the other 
hand, may show the dangerous quality of cracking or 
swelling. This shows itself in a strong expansion, 
which destroys the cohesion of the mortar and may 
cause its total destruction. Cement which swells badly, 
if laid between retaining walls, shows an immense 
power of expansion, even to the extent of forcing out 
the stones of the masonry. 

The swelling does not show itself until after the set- 
ting. The worse the fault is the sooner it will appear. 
It shows itself, also, sooner in water than in air. In 
pats of cement kept under water this defect is to be 
noticed in the appearance of fine net-like cracks, or in 
worse cases in curving of the pats and the appearance 
of cracks around the edges. It is characteristic of 
expansion cracks that they run from the edges toward 
the center of the pat and are widest at the edges and 
narrower toward the center. These expansion cracks 
should not be confused with shrinkage cracks, mention 
of which will be made later. 

The swelling of cement is always due to defects in 
manufacture. These are: 

1. Faulty composition of the raw material, especi- 
ally too high a proportion of lime. 

2. Imperfect preparation of the raw material. 

3. Imperfect burning of the clinker. 

4. Too high proportion of sulphate or magnesia. 
According to the German oflScial requirements, a 

cement is considered to be constant in volume if a pat. 



SHRINKAGE-CRACKS AND HAIR-CRACKS. 13 

kept 28 days under water, remains perfectly flat and 
free from cracks. Swelling, due to too much lime, 
shows itself in this test with certainty within a few 
days or weeks. Cement containing too much magnesia, 
however, and burned to the point of sintering, shows 
noticeable expansion only after the lapse of long peri- 
ods, extending even to several years. Only chemical 
analysis, or the guarantee of the manufacturer, can 
afford protection against the danger of expansion from 
excess of magnesia. Experience has shown that the 
presence of magnesia up to 3 per cent is entirely harm- 
less. 

In conclusion, two other peculiar appearances may 
be mentioned which are often erroneously considered 
to indicate swelling of the cement. 

It is sometimes noticed that pats of neat cement, 
left in air, lose considerably in strength, and after a 
certain time become soft or friable, while similar pats 
kept in water are faultless in all respects. This is espe- 
cially liable to occur in the case of pats made very wet 
and allowed to dry out immediately after setting. If, 
on the other hand, the pats are kept moist during th» 
first stages of hardening, this defect is not developed. 

Cracks, similar to those produced by swelling, are 
also produced when pats or briquettes are placed in 
water too soon^ or before the setting is complete. To 
prevent this the official requirements specify that test- 
pieces shall be kept 24 hours in moist air before placing 
in water. 

SHRINKAGE-CRACKS AKD HAIR-CRACKS. 

Portland cement mortar without sand, exposed to the 
air, diminishes in volume. If the drying takes place 
gradually and uniformly, as in a closed room, the 
cement shows no defects. Too rapid drying, in draughts 



14 RESISTANCE TO WEATHER. 

of air or in sunshine, without the precaution of keeping 
the cement moist, causes so-called shrinkage-cracks. 
These may be distinguished, in pats of cement, from 
expansion-cracks by the fact that they appear during 
the setting and show themselves as irregular curved 
lines extending over the middle of the pat. As already 
stated, the formation of shrinkage cracks is due to 
faulty use of the cement, and has practically nothing to 
do with its quality. Very finely ground cements are, 
moreover, more likely to show hair-cracks than those 
which are more coarsely ground. 

Hair-cracks appear as fine lines on cement work 
which has stood some time. They are especially to be 
noticed on cement which has lain in the open air, and 
are due to frequent changes between wet and dry con- 
ditions. Hair-cracks and shrinkage-cracks occur chiefly 
when pure cement or mortar too rich in cement is used. 
They may be certainly avoided by the addition of suflS- 
cientsand and suitable treatment of the work. 

RESISTANCE TO WEATHER AND REHAVIOR UNDER EXTREME 
HEAT AND COLD. 

Mortar made from pure cement is, strictly speaking, 
not weatherproof, owing to its tendency to form shrink- 
age-cracks and hair-cracks. Repeated expansion and 
shrinkage increases the number and size of these cracks, 
until finally under the action of water and frost the 
cement breaks to pieces. Complete weather-resisting 
qualities can be given to cement mortar only by the 
the addition of sand. One part sand to one part cement 
will be found sufficient. 

The temperatures which are reached in warm, or 
even hot, climates have no bad influence on the harden- 
ing of Portland cement. The only precaution necessary 



BEHAVIOB UNDER EXTREME HEAT AND COLD. 15 

is to see that the water necessary for hardening is not 
removed too soon; or, in other words, that the work is 
kept sufficiently moist during the earlier stages of hard- 
ening. Even the temperature of boiling water is harm- 
less to the strength of Portland cement, and a heat of 
400 degrees to 500 degrees F. may be borne without in- 
jury. At a red heat it becomes soft and friable. Never- 
theless it has been proved by long experience with 
Portland cement concrete that this material shows a 
high degree of strength and safety when exposed to fire. 
Portland cement is less affected by frost than any 
other hydraulic material; If the cement is once fully 
set it may be exposed to strong freezing without any 
ill effect. It is only during the setting that injury can 
take place, and this is chiefly to be feared in case the 
mortar was made too wet, so that the freezing of the 
water forces the mass asunder. If water is sparingly 
used, masonry and concrete work may be done in 
extremely cold weather with good results. It must be 
remembered, however, that the setting and hardening 
of cement are much delayed by cold. Cement work 
done in freezing weather shows, therefore, but little 
strength at first, but finally reaches its normal hardness. 
Addition of salt to mortar in cold weather is generally 
to be avoided on account of the unsightly efflorescences 
which often result. It is better, when work in extreme 
heat or cold cannot be avoided, to warm the water 
and sand used and to reduce the water to the small- 
est possible quantity in order to hasten the setting of 
the mortar. If care is taken to allow no free water to 
separate, or that any excess of water is absorbed by dry 
stone, there is nothing to be feared even from extreme 
eold. Surface plastering with cement should, how- 
ever, not be attempted in freezing weather. 



16 ACTION OF SEA WATEB. 

On mixing cement with sea water the setting is 
delayed and decreased strength results. This is chiefly 
due to the action of the magnesium sulphate and chlor- 
ide of the sea water on a portion of the cement; the 
hardening value of this part is therefore lost and the 
strength !:ttained is less than with the use of fresh 
water. One might suppose that this action of the sea 
water salts would cause the strength of the cement to 
continue to fall off and that the work would finally 
fall to pieces. This is, however, not the case, owing to 
the fact that the penetration of the sea water into the 
mass is prevented by the great and constantly increasing 
density of the Portland cement mortar. A deposit of 
magnesia is also formed in the pores of the mass, and 
gives further protection against the entrance of the 
sea water. Portland cement is therefore unequalled 
for marine constructions. In all cases in which this 
work has been intelligently done Portland cement con- 
crete has fulfilled all requirements most satisfactorily. 
In work exposed to sea water it is of the highest 
importance to give the concrete as dense and close- 
grained a surface as possible, since only such a surface 
is capable of permanently resisting the chemical action 
of the salt water and the mechanical force of the waves. 

Portland cement is especially suitable for work of 
this kind, since uniform tests of tensile and compres- 
sion strength are a guarantee of a uniform material 
which can safely be relied upon. This is by no means 
true in the case of puzzuolana cements, so-called slag 
cements and hydraulic limes, which are often of very 
variable quality. 

ADDITIONS AND ADULTEBATIONS. 

Substances added to Portland cement may be divided 
into those which are intended to give it certain valuable 



ADDITIONS AND ADULTERATIONS. 17 

qualities, and others which are added for the purpose 
of fraud. In the first group are found gypsum and 
coloring matters. 

The addition of gypsum (sulphate of lime) which 
should not exceed 2 per cent, is made for the purpose 
I of causing naturally quick-setting cements to set more 

slowly. In this way the quality of the cement is 
improved and its strength increased. Additions of a 
higher proportion of gypsum are not admissable, as it 
tends to cause swelling. 

Coloring matters are sometimes added to cement in 
order to make it suitable for decorative purposes. 
Mineral colors are practically always used. To give the 
cement a somewhat darker tint, especially for use in 
making cement wares, a few per cent of lamp-black 
is added. Nearly all coloring matters reduce the 
strength of the cement; ultra-marine, however, in small 
quantities, increases it. The red iron oxide of com- 
merce, often used to produce a red color, frequently 
contains a considerable amount of sulphuric acid, and 
may cause swelling. Care should be taken in the 
choice of the coloring matters employed. 

In regard to the production of white Portland cement 
it may be said that this has not hitherto proved success- 
ful, on account of impurities contained in the raw 
materials or derived from the fuel. The so-called 
white cements of commerce are for the most part 
inferior products which do not deserve the name of 
Portland cement. In consequence of its gray color, 
Portland cement cannot be made white by the addition 
of pigments. 

From fraudulent and avaricious motives, blast furn- 
ace slag, limestone, shale, basalt, ashes, sand, etc, aro 
added to cement. These are simply adulterations, 



18 PACKING AND WEIGHT. — SEASONING. 

which always injure the quality of the product. These 
substances may be more or less easily detected, and 
their use, in consequence of the close watch kept by 
the association upon the product of its members, has of 
late practically ceased. 

II. USE OF PORTLAND CEMENT. 
PACKING AND WEIGHT. 

(American weights are here substituted for the German weights 
given in the original pamphlet. — Tbanslator.) 

Portland cement is packed in barrels and sacks. The 
barrel is of 400 lbs. weight and contains 380 lbs. (about 
3 J cubic ft.) of cement. Sacks are generally one-fourth 
barrel, or 95 lbs. Since empty barrels and sacks are 
received by the manufacturer at a certain price, care 
should be taken to preserve them in an orderly manner. 
Empty sacks are most conveniently returned in bundles 
of ten each. 

Barrels and sacks should be marked by the manu- 
facturer with name, trade-mark and gross weight of 
package. Loss by sifting out and variations from 
standard weight to the amount of 2 per cent are allow- 
able. 

STOBAGE (SEASONING) OF CEMENT. 

Storage of cement improves its quality. If well pro- 
tected and kept dry the cement gains in strength and 
becomes more slow-setting and more constant in vol- 
ume. This so-called seasoning results from the action 
of the moisture and carbonic acid of the air. At the 
same time, owing to the disintegration of the coarser 
grains, the cement increases in fineness. If, however, 
cement is stored in a damp place it becomes caked, 
lumpy, partially set, and finally worthless. Dealers 
should keep this in mind and, give close atten- 



CHOICE OF CEMENT. 19 

tion to the choice of a suitable place for btorage. 
Portland cement bears long storage well, and even if 
packed in sacks may be safely kept in a dry place for 
many months. 

If fresh, insufficiently seasoned cement is packed, an 
increase of volume takes place on long storage, and if 
the barrels are too completely filled or the hoops too 
strongly driven the hoops may be broken or the staves 
bent out. This may occur with faultless cements, and 
has nothing to do with so-called swelling or cracking. 

CHOICE OF CEMENT AND CONCRETE MATERIALS. 

Quick-setting cements are used for work exposed to 
leaching water, also for plastering and casts. For 
all other purposes slow-setting cement is preferable. 
Neat Portland cement is rarely used for mortar, and 
only in case the work is to remain constantly under 
water or in damp earth. In other cases more or less 
sand must be used to prevent shrinkage-cracks and 
produce a weatherproof mortar. 

The character of the sand, gravel and stone used has 
great influence on the strength of the work. The sand 
must be sharp and pure; if it contains clay this must 
be removed by repeated washing. Very fine sand is 
generally objectionable; the best results are obtained 
with a graded sand, consisting of grains of various 
sizes, from fine to coarse. Stone and gravel for con- 
crete must also be naturally clean or well washed, and 
must not be soft or chalky. Only clean water, free 
from mud, should be used for mixing cement mortar. 

PREPARATION AND USE OP MORTAR. 

If good results are to be obtained with Portland 
cement great care must be taken in the preparation of 
the mortar. If vessels which have been used for lime 



20 PREPARATION AND USE OP MORTAR. 

or contain set cement are employed these must be 
well cleaned before use. As cement and sand are 
mixed in proportions by measure, it is a good plan 
to provide measuring vessels corresponding to the vol- 
ume of the cement packages. The necessary figures 
are given in a previous paragraph under "Packing and 
Weight." Guess-work mixtures should never be made, 
for such methods not only give mortar of varying com- 
position, but also cause unnecessary waste of cement. 

The proportion of sand to be used varies with the 
character of the work*; 1 to 2 parts sand to 1 cement 
are used only for work requiring extraordinary strength, 
great resistance to wear, or impermeability to water; 3 
to 4 parts sand to 1 part cement are employed for 
ordinary weatherproof plastering, building mortar, 
foundations, artificial stone, etc. 

More or less water should be taken according to the 
rate of setting of the cement, conditions of temperature, 
and kind of work in view. As a general rule as little 
water as possible should be used, and the mortar made 
plastic by prolonged, vigorous mixing. For the prep- 
aration of mortar the measured quantity of sand is 
spread out and the correct amount of cement scat- 
tered evenly over it; the two materials are then thor- 
oughly mixed together. The necessary quantity of 
water is then strongly and thoroughly worked into the 
mass. 

One of the chief rules in preparing mortar is that 
cement which has become set should never be worked 
up anew with water. For this reason no more mortar 
should be mixed at one time than can be used before 
the setting begins. Mortar which has become set and 
is again made plastic with water will never gain its 
normal hardness. Another important point is that the 



CEMENT- LIME MORTAR. 21 

brick or stone used for building must be thoroughly 
wetted before being laid up with cement mortar. The 
work should also be kept damp for a considerable time 
after it is finished, in order that the mortar may reach 
its full, stone-like hardness. The common practice of 
wetting bricks just before use by sprinkling with water 
from the mason's brush is quite insufficient. The bricks 
should be kept under water, in a vessel, until thoroughly 
saturated, and a stiff mortar used, in order that the 
brick should not be displaced after laying. 

OEMENT-LIME MOETAR. 

There are many kinds of work which require a quick- 
hardening mortar, but for which the great strength of 
a mixture of 1 cement with 1 to 4 of sand is unneces- 
sary. The cost of such mortar is also, for many pur- 
poses, too high. A mixture of cement with 5 or more 
parts sand would give abundant strength, but such 
mortar works too " short '' and adheres too imperfectly 
to the brick or stone ; it cannot, therefore, safely be used. 

In such cases the addition of slaked lime or hydraulic 
lime will correct the faults of poor mixtures of cement 
and sand, and will produce a cheap mortar, suitable 
for a great variety of uses. The addition of slaked 
lime allows the full advantage to be obtained from the 
use of good Portland cement, and makes it possible for 
this material to compete in price with cheaper hydraulic 
materials. Used in this manner, Portland cement may 
be employed with economy for the most ordinary pur- 
poses. The advantages of Portland cement lime mortar 
are its cheapness in comparison with other hydraulic 
materials, it rapid hardening, marked hydraulic prop- 
erties, great strength on exposure to air, and remark- 
able resistance to weather. 



22 POKTLAND CEMENT MOETAR IN WATER AND AIR. 

The following mixtures for cement-lime mortar have 
been found by experience to be most suitable: 

Cement 1, sand 5, lime paste %. 

1, " 6 to 7, *' " 1 

1, " 8, " " IK 

" 1, " 10. " " 2 

The above proportions are to be taken by measure. 
Hydraulic lime may be used in place of ordinary slaked 
lime. 

Cement-lime mortar is prepared by making a dry 
mixture of the required quantities of cement and sand; 
milk of lime is then made with the necessary quanti- 
ties of lime paste and water, and this milk of lime 
thoroughly mixed and worked in with the mixture of 
cement and sand. 

The great advantages of cement-lime mortar for a 
multitude of purposes deserve to be more widely 
recognized than they are at present. 

PORTLAND CEMENT MORTAR IN WATER AND IN AIR. 

On account of its remarkable hydraulic properties, 
great strength, and durability, Portland cement mortar 
gives excellent results both in water and in air. The 
first essential to success is, however, that the mortar 
should be prepared and used suitably and intelligently 
for the special purpose in view. For work to be 
exposed to water, care must be taken to produce as 
dense and impenetrable a surface as possible; this may 
be accomplished by mixing the materials in suitable 
proportions. Ornaments, casts, etc., which are to be 
exposed to weather must never be made from pure 
cement; the same may be said of architectural artificial 
stone work. A certain proportion of sand must always 
be added. 



WATER-TIGHT MORTAR. 2o 

In the preparation of water-tight mortar it should be 
remembered that the richer the mixture is in cement 
and the longer the mortar hardens the greater will be 
it impermeability to water. The reason of this is that 
in the process of hardening the mortar becomes con- 
stantly more dense, and the pores gradually close. 
The porosity of mortar is the greater, the thinner the 
layer employed and the higher the proportion of sand 
used. Coarse sand, also, gives a more porous mortar 
than fine sand. For a coating f to | of an inch in 
thickness which requires to be immediately water- 
proof, the following mixtures are recommended: 

Cement, 1, sand (not too coarse), 1 

" 1, " 1, lime paste >^ 

1, " 3, " " 1 

" 5, " " IM 

" 6, « « 2 

Which of these mixtures is to be employed depends 
on the nature of the work. By the addition of gravel 
or broken stone to the above mixtures water-tight con- 
crete is obtained. From motives of economy, however, 
it is customary to make only the surface of the concrete 
of water-tight composition. 

CEMENT PLASTERING AND PAINTING. 

Experience has shown that cement plastering on walls 
and cornices, even when made with faultless material, is 
not always permanent. Sometimes the surface scales 
off in thin layers; in other cases blisters form and crack, 
or the whole layer of plastering may separate from the 
wall and fall off. In all such cases the work, and not 
the cement, is at fault. If walls are to be plastered with 
cement mortar it is indispensable that the surface be 
previously thoroughly cleaned from dust, dirt or lime- 
mortar, washed and repeatedly wetted. If the wetting 



24 CEMENT PLASTBBING AND PAINTING. 

is insufficient the dry stone or brick take away from 
the cement the water necessary for hardening; if this 
happens the mortar adheres badly and never reaches 
its proper hardness. Wall-plastering which is exposed 
to weather should never be made very rich in cement 
for fear of the formation of shrinkage cracks. The 
more sand is used, provided the necessary strength is 
obtained, the better the plastering will resist the 
weather. Fine sand should be used, and for the pur- 
pose of avoiding hair-cracks and shrinkage cracks it is 
best to finish the surface with a felt polisher instead of 
a trowel or steel tool. 

Cement plastering must be kept moist and pro- 
tected from wind and sun. This work can be done 
most advantageously in spring; frost should be espec- 
ially avoided. Some sands contain little particles of 
coal which are scarcely visible to the eye; these may 
have a very bad effect on the appearance of the work. 

Cement work which is to be painted, either on account 
of hair-cracks or efflorescences derived from the alkal- 
ies and lime of the cement, or from any other cause, 
must be fully hardened and thoroughly dry. It is 
prudent to let the work stand a year before oil paint is 
applied. To insure the durability of the painting 
several methods may be used. 

1. The surfaces are repeatedly brushed over with 
dilute sulphuric acid (1 part strong acid to 100 parts 
water), and allowed to dry before the paint is applied. 

2. The surfaces are repeatedly and carefully washed 
with water, then after 8 days, saturated twice with lin- 
oleic acid (to be had from any druggist). After a few 
days, when the surface has grown hard, the oil paint is 
applied. 

3. An excellent preparatory coating for oil paint is 



CONCRETE. 25 

a solution of common water-glass in 3 or 4 parts water. 
After two applications the surface is washed with water; 
after a short time the water-glass is again applied. 
When dry the paint can be used. 

Even oil paint is, however, often of slight durability 
when exposed to weather. For work of great perman- 
ence the patent process of Dr. Golinelli, Koch and 
Adamy of Darmstadt, for preparation of cement work 
for stereochromatic painting, may here be mentioned. 

OONGRETE. 

One of the most important uses of Portland cement 
is in the making of concrete. This is a mixture of 
cement with sand and gravel or broken stone, with the 
addition of the necessary water. To obtain good ad- 
hesion of the materials, the water, sand and stone must 
all be clean; in some cases washing of these materials 
may be necessary. 

The gravel or stone used must be at least equal in 
hardness to the cement mortar. Good gravel, basalt or 
hard lime stone are most suitable; soft sandstone or 
broken brick are to be avoided. The stone should not 
be above egg size. The proportions to be used depend 
on the nature of the work. When once determined 
they should be rigidly adhered to. For the preparation 
of concrete, the cement and sand are well mixed 
together on a dry platform; enough water is then mixed 
in to make the mortar about as moist as damp garden- 
earth; the gravel or stone, previously well wetted, is 
then added, and the whole thoroughly mixed by 
repeatedly turning over with shovels. The proportion 
of water must be so regulated that after prolonged and 
vigorous stamping the mass will become elastic and 
show a little water on the surface. The use of more 



26 PREPARATION OF CONCRETE FLOORS, ETC. 

water is to be ayoided, since it makes the mass less 
dense and lowers its strength. Too great stress cannot 
be laid upon thorough and careful stamping of the con- 
crete into place, since in no other way can great strength 
and density be obtained. 

With good Portland cement the proportion of 1 part 
cement and 3 parts sand, with varying amounts of 
gravel or stone up to 9 parts, will be found suitable; 
for some purposes poorer mixtures may be used. 

Portland cement concrete finds many useful applica- 
tions in constructions both above and below ground; 
for example, in foundations of all kinds, sidewalks, 
ceilings, walls, arches, cement wares, etc. 

PREPARATION OF OONORBTE FLOORS, SIDEWALKS, STEPS 
AND CEILINGS. 

For the construction of durable cement floors or side, 
walks the foundation must be suitably prepared. For 
outdoor work on yielding ground a porous layer, at 
least 10 inches thick, of coarse gravel or slag should be 
laid, well rammed down and leveled. For indoor work 
on dry ground it is sufficient to level the surface and 
stamp it down firmly. Floors and sidewalks are gen- 
erally built in two layers; a lower bed of concrete 2^ 
to 4 inches thick, and a surface coat of richer mortar 
of a thickness of f to f of an inch. 

The concrete layer may be made richer or poorer 
according to the service which the work must undergo. 
For heavy duty a mixture of cement 1, sand 3 and gravel 
6 is recommended. In less important work cement 1, 
sand 5 and gravel 10 will answer. A suitable mixture 
for ordinary requirements is, cement 1, sand 4 and 
gravel 8 or broken stone 6. 

The surface layer consists of cement 1, sand 1, and 



PREPARATION OF CONCRETE FLOORS, ETC. 27 

must be spread over the concrete before the latter has 
set. Before spreading the top layer the concrete should 
be freed from loose material and its surface roughed 
up. The mortar is spread with a straight-edge and 
when sufficiently hardened is finished with a wooden 
tool. A grooved roller is used to produce a ribbed sur- 
face, especially in side-walk work. 

When the work is finished and the cement is well set, 
the surface is carefully covered with a layer of sand 4 
inches in thickness. This is moistened and kept in 
place for several weeks if possible. Only in this way 
can the formation of hair-cracks be prevented and a 
well hardened surface obtained. 

Cement expands and contracts with changes of tem- 
perature, in the same way as iron, wood, sandstone and 
other materials. From this cause, if the necessary care 
has not been taken in the work, cracks will result, 
especially in wide surfaces. These may be avoided by 
dividing the flooring into smaller blocks, which should 
not exceed 4 to 5 square yards in area, and should be 
separated by strips of tar paper or by sand joints f inch 
in width. The joints in the concrete must correspond 
with those cut in the surface layer. The division of 
the work into blocks is also to be recommended in con- 
crete walls and curbs. 

One of the most strikingly successful applications of 
Portland cement in building is its use for ceilings and 
staircases. Safety against fire, freedom from dry-rot, 
quickness of construction, and cheapness are some of 
the many advantages presented by this type of con- 
struction. A description of this and other similar 
applications of cement would, however, extend this 
pamphlet beyond desirable limits. Reference must, 
therefore, be made to special works on this subject.* 



28 NOTES ON CEMENT WORK AND ITS TREATMENT. 

As already stated, cement work must be protected 
from too rapid drying out, since from this cause shrink- 
age cracks and lack of hardness and strength may 
result. A certain amount of water is absolutely neces- 
sary for the proper hardening of cement. 

In case of sidewalks, ceilings, etc., the surface is to 
be kept covered with damp sand as long as possible. 
Cement wares should be kept under water, or stored in 
damp rooms, free from currents of air, and frequently 
sprinkled. Wall-plastering should be kept covered as 
long as possible with wet sacks or cloths. Cement 
casts which are to be exposed to weather, such as 
statues and architectural ornaments, must never be 
made of pure cement; a suitable proportion of sand is 
necessary, even for the surface. By the addition of 
fine, sharp sand the formation of unsightly hair-cracks 
is avoided without injury to the appearance of the 
work. The use of quick-setting cement with too little 
sand and much water, taking the objects too soon out 
of the moulds, and their delivery before they have 
acquired the necessary hardness, are serious errors. 
Such treatment was formerly much more common than 
it is at present, and has done much to cause cement 
wares to be regarded with undeserved suspicion. Since 
the introduction of more rational methods of manu- 
facture, casts in cement have given full satisfaction, 
and owing to their cheapness are rapidly coming into 
extensive use. Architectural details for which sand- 
stone was exclusively used twenty years ago, are now 
extensively cast in cement and find application in edi- 
fices of the most highly artistic character. 



♦Portland cement und seine Anwendungen im Bauwesen; Berlin, 1892. 
'~'ement in seiner Verwendung im Hochbau; Liebold, Halle, 1875. 



CONCLUSION. 29 

In conclusion it may be noted that the remarkable 
properties of Portland cement make it suitable for an 
endless variety of uses. It is hoped that this brief 
sketch may serve to bring this valuable material into 
more extensive notice, and to contribute to a wider 
appreciation of its qualities and capabilities. 




MAR 19 1§04 




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